This invention relates to switched reluctance motors and more particularly, to a switched reluctance motor having an improved rotor design which reduces flux path lengths and utilites all salient poles thereby increasing power density and reducing motor losses.
Switched reluctance motors are well-known in the art. Typically these are multi-pole motors having poles or teeth on both the motor stator and rotor. The motor also has phase windings on the stator but not on the rotor. In addition, the rotor has saliency so formed as to produce synchronous motor operation. In operation, the rotor rotates to bring a pair of rotor poles into a minimum reluctance position with respect to a pair of stator poles. Currents in the motor are unipolar, flowing through the stator windings in only one direction. For such motors, a reversal of direction is achieved by changing the sequence in which windings are energized during a motor revolution. The advantage of reluctance motors is that they are efficient in converting electrical energy into mechanical work, and are reliable because of their mechanical simplicity.
Among the design considerations involved with switched reluctance motors are such things as the power densities which can be developed with a particular configuration, the amount of iron or other magnetic material which must be used in the motor, starting characteristics of the motor, etc. Rotor design has particular importance in these areas, especially with respect to such factors as the construction of the rotor teeth and the rotor core, and the size of the air gap between the rotor and stator. Different rotor designs are known. See, for example, U.S. Pat. No. 3,062,979. There, rotor teeth are formed by interspersing sheets of magnetic material with non-magnetic material. Such an approach is of interest because it reduces the amount of magnetic material required in the motor construction. However, other approaches may be more economical, not only with regard to construction of the rotor's teeth, but to also further reduce the amount of magnetic material in the motor, improve its efficiency, and permit it to be smaller in size than prior switched reluctance motors.